Recently, to avoid various problems caused by eating too much animal food, low-calorie foodstuffs have been drawing public attention as healthy food. In addition, the relation between food and prevention of diseases has been clarified, and it is known, for example, that those containing fibers and less fat help to reduce risks of cancer, and those containing fibers and less cholesterol reduce risks of coronary heart diseases. Thus, healthy food that helps to maintain and promote human health attracts public attention, and such food that is rich in protein and low in calories and contains dietary fibers and the like is studied, and sold in the market.
Although various healthy foods have been studied and commercialized as described above, because the term, "healthy food", has not been clearly defined, and has for different meanings, it has caused a problem that misunderstanding or confusion on the part of consumers In order to solve the problem, the U.S. Food and Drug Administration (FDA) has established a guideline stating, if total fat, saturated fat, cholesterol and sodium contained in a serving size of a particular foodstuff are higher than specified levels, the foodstuff cannot be claimed as being a healthy food. More specifically, a foodstuff of a meal type, for example, cannot be claimed as being healthy food, if total fat of 26.0 g or more, saturated fat of 8.0 g or more, cholesterol of 120 mg or more and sodium of 960 mg or more are contained in a serving size of the particular foodstuff. In the case of packaged foodstuffs, a nutritional specification showing contents of ingredients must be provided as well.
Of the above-mentioned healthy foods, those using a soybean protein instead of animal meat protein are very important to prevent intake of excessive fat and calories. Since a soybean protein is particularly excellent in the balance of essential amino acids, and very nutritious, a variety of foodstuffs rich in protein and low in calories with a soybean protein contained-as a protein source are studied. As a part of such study, addition of a soybean protein to such puffed food as bread has been also studied. In a puffed food like bread which is made from such milled grains as wheat flour, starches and such expanding agent as yeast and baking powder, if a soybean protein is used entirely or partly in place of such material as wheat flour, the puffed food obtained is low in loaf capacity and gives a tough touch, when it is eaten, so a foodstuff that sufficiently satisfies the human taste has never been obtained. In order to solve the problem, the inventors proposed a method of obtaining a bread-like puffed food that comprises a soybean protein, wheat flour and eggs, and that has a high content of soybean protein by puffing a dough using an expanding agent (see Japan Laid-open Pat. No. 144936/1989).
The puffed food produced by such method as disclosed in the laid-open patent is high in loaf capacity, excellent in touch, flavor and nutritional balance, and is favorably accepted in Japan, United States and many other countries. However, has the problem that the puffed food obtained in such manner contains much cholesterol, and fails to meet the above-mentioned FDA specification, because eggs that are high in cholesterol content are used as a foaming agent for improving the touch and the puffing effect. It is another problem that the food cannot be served to those who are religiously prohibited from eating eggs. Additionally, use of chemical expanding agents has been a problem as well.
In the light of such problems, it is an object of the invention to provide a method for producing a food superior in flavor, touch and nutritional balance, low in cholesterol content, and containing a soybean protein and dietary fibers and a dough for such puffed food.